The long term objectives of this project are to delineate the role of the cellular immune response in the pathogenesis of filarial lymphadenopathy and to identify the T-cell regulatory mechanisms which prevent severe lymphadenopathy in most infected individuals. Repeating, severe episodes of lymphadenopathy in a minority of people infected with Brugia sp. and Wuchereria bancrofti corelate with the development of the lymph edema and, eventually, disabling and disfiguring elephantitis. The dog, infected with its natural parasite, Brugia pahangi, has long been known to manifest clinical signs of lymph edema in a minority of infected individuals and to demonstrate localized lymphadenopathy of varying severity. In addition, because of its large size among laboratory animals, the dog has been used most extensively for physiology studies of lymph nodes and ducts of limbs. Therefore, the specific aims of this project are: (1) to characterize changes in the cellular immune responses occurring in infected and noninfected popliteal lymph nodes of chronically infected low and high responding dogs exposed to local node perfusion with adult B. pahangi products; (2) to test the ability of suppressor T lymphocytes, transferred from infected nodes to noninfected nodes. to modulate these responses in vivo; and (3) to identify specific antigens of B. pahangi that stimulate blastogenesis in responder dog lymph node cells in vitro and in nonresponder dog lymph node cells depleted of suppressor cells. Popliteal node tissues, obtained by serial biopsies, will be compared based on analysis of histology, immunohistology, cell proliferation assay and flow cytometry (FCM) using monoclonal antibodies against dog immune cell subsets and polyvalent antisera against dog IgG, IgE, and parasite antigens. Draining lymph will be analyzed for parasite antigen specific IgG and IgE antibodies. If results from specific Aim #1 indicate infected node restricted suppressor T lymphocyte action in low responding dogs, then this restriction will be tested in vivo by transferring suppressor T lymphocytes (selected by "panning" and FCM using monoclonal antibody E-11) from infected nodes in regression to noninfected nodes being perfused with parasite products. If results from #1 indicate systemic suppression or tolerance, then breaking suppression or not breaking tolerance by transfer of helper T (DT-2 positive) lymphocytes will indicate suppressor T lymphocyte action or strict B or T lymphocyte tolerance, respectively. Analysis of node biopsies and draining lymph, as described above, will be used to evaluate the activity of transferred suppressor T and helper T cells in the perfused node. Brugia adult worm products fractionated by HPLC or affinity purified from dog serum will be isolated based upon their ability to stimulate blastogenesis in responder dog node cells and induce suppression or tolerance in nonrespondents.